The infrared (900-1100 cm-1) Faraday rotation and circular dichroism are measured in the normal state of underdoped High Tc superconductors and used to study the magneto-transport. YBa2Cu3O6+x thin films are investigated in the temperature range 10-300 K in magnetic fields up to 8 Tesla and as a function of oxygen concentration. A dramatic increase of the Hall frequency is observed for underdoped samples which is not consistent with the approach to a Mott transition but is consistent with a partial gapping of the Fermi surface as predicted in charge density wave models.
@article{arxiv.cond-mat/0309108,
title = {Magneto-optical evidence for a gapped Fermi surface in underdoped YBa2Cu3O6+x},
author = {L. B. Rigal and D. C. Schmadel and H. D. Drew and B. Maiorov and E. Osquigil and J. S. Preston and R. Hughes and G. D. Gu},
journal= {arXiv preprint arXiv:cond-mat/0309108},
year = {2009}
}